Local ordering and electronic signatures of submonolayer water on anatase TiO2(101)

Y. He, A. Tilocca, O. Dulub, A. Selloni, U. Diebold

Department of Physics, Tulane University, New Orleans, Louisiana 70118, U.S.A.
Department of Chemistry and Materials Simulation Laboratory, University College London, London WC1H 0AJ, UK
Department of Chemistry, Princeton University, Princeton, New Jersey 08544, U.S.A.
Faculty of Material Science and Engineering, Hubei University, 430062 Wuhan, Hubei, China

Nature Materials 8 (2009) 585-589

The interaction of water with metal oxide surfaces is of fundamental importance to various fields of science, ranging from geophysics to catalysis and biochemistry. In particular, the discovery that TiO2 photocatalyses the dissociation of water has triggered broad interest and intensive studies of water adsorption on TiO2 over decades. So far, these studies have mostly focused on the (110) surface of the most stable polymorph of TiO2, rutile, whereas it is the metastable anatase form that is generally considered photocatalytically more efficient. The present combined experimental (scanning tunnelling microscopy) and theoretical (density functional theory and first-principles molecular dynamics) study gives atomic-scale insights into the adsorption of water on anatase (101), the most frequently exposed surface of this TiO2 polymorph. Water adsorbs as an intact monomer with a computed binding energy of 730 meV. The charge rearrangement at the molecule-anatase interface affects the adsorption of further water molecules, resulting in short-range repulsive and attractive interactions along the [010] and [11-1]/[1-1-1] directions, respectively, and a locally ordered (2x2) superstructure of molecular water.

Reprints available from U. Diebold (diebold at iap_tuwien_ac_at).

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